1. Field of the Invention
The present invention relates to an infrared ray sensing element provided with a thermopile, and a method of producing the infrared ray sensing element.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. 2000-111396 (=JP2000111396) discloses a conventional infrared sensing element and its manufacturing method. Specifically, JP2000111396 discloses a thermopile-type infrared ray sensing element. There is provided an infrared ray absorber on a center upper face of a substrate and a beam is used for supporting the infrared ray absorber to the substrate, thereby the infrared ray absorber is heat-isolated from the substrate.
FIG. 1A and FIG. 1B show a structure of a beam of the conventional infrared ray sensing element like that according to JP2000111396, specifically, FIG. 1A shows a perspective view of a beam 120 and FIG. 1B shows an upper face of the beam 120. In FIG. 1, the beam 120 has two polysilicons 121, 122 each serving as thermopile, specifically, an N-type polysilicon 121 and a P-type polysilicon 122 are formed in parallel to each other in a longitudinal direction of the beam 120. The N-type polysilicon 121 and P-type polysilicon 122 are covered with a protective film 123 made of silicon oxidized film and the like, with the beam 120 shaped rectangular.
When an external bending force is applied around a first center line b1 in FIG. 1B, the beam 120 is deformed as shown in FIG. 2A taken in the direction II-A in FIG. 1B. In this case, most of the above bending is caused to the protective film 123 since the N-type polysilicon and P-type polysilicon 121, 122 (thermopiles) are harder than the silicon oxidized film of the protective film 123. Meanwhile, when an external torsional force is applied around a second center line b2 in FIG. 1B, a sheer stress caused by the torsional force deforms the beam 120 as shown in FIG. 2B taken in the direction II-B in FIG. 1B. When the beam 120 has a bent portion between the substrate and the infrared ray absorber, displacement of the beam 120 in a height direction (Z-direction) is increased.